Common mobile robot and/or vehicle uses, such as search-and-rescue, police, toy, and military applications, require good performance in both urban and natural environments. The surfaces and obstacles seen in these environments change form one region to the next. Some regions include mostly smooth and flat ground. Other regions include obstacles that must be crossed, or loose, shifting material. This terrain variation makes navigation difficult for conventional wheeled vehicles, wheeled robots, and conventional wheeled radio controlled vehicles.
Conventional wheels are often designed specifically for the terrain of one region, which results in less than ideal performance in other terrain. Wheels designed for smooth terrain are often not able to effectively overcome large obstacles and rough terrain. Wheels designed for overcoming large obstacles, for example, wheels of non-uniform shape such as legged-wheels, are often less efficient over smooth surfaces than wheels intended for smooth surfaces. The lack of a singular wheel design that can equally effectively navigate terrain suggests a need for a wheel that can transform as needed to best accommodate the particular terrain to which it is subjected.
Generally speaking, a transformable wheel can alter its shape and dimensions (e.g., diameter) to better handle changing terrain. When round, a transformable wheel can move quickly and efficiently over flat ground. When the wheel shape transforms too non-circular, a transformable wheel can better grip and clear obstacles. Thus, a transformable wheel can significantly increase the versatility of a wheeled mobile robot or another wheeled vehicle.
Various transformable wheel designs are known. However, when a conventional transformable wheel increases in diameter, the weight of the robot/vehicle to which the wheel is installed must be lifted as the wheel expands. The transformable wheel, the mechanism by which wheel transformation is accomplished, and the actuator driving the mechanism and causing the transformation, must be able to overcome the weight of the robot/vehicle and withstand the forces caused by lifting the robot/vehicle during expansion of the wheel. At a minimum, this puts stress on the wheel and the mechanism that transforms the wheel.
In light of the deficiencies revealed by the foregoing comments, it is desirable to provide a transformable wheel and a method of wheel transformation by which the transformation actuation forces and the stresses on the transformable wheel are reduced. It is also desirable to provide a transformable wheel and a method of wheel transformation that permits wheel transformation even when a robot or vehicle to which the wheel is installed of significant weight and/or is carrying a heavy load.